Vacuum regulator for maintaining a substantially constant vacuum in a vacuum system

ABSTRACT

The invention relates to a vacuum regulator ( 1 ) for maintaining a substantially constant vacuum in a vacuum system ( 2 ). The vacuum regulator ( 1 ) includes a main valve arranged to control a supply of air to the vacuum system ( 2 ). The main valve includes a valve seat ( 3 ) defining a passage ( 4 ) arranged to lead air to the vacuum system ( 2 ) and a valve body ( 5 ) moveably arranged in a direction between a closed position and a maximally open position in order to regulate the size of a minimum flow area ( 18 ) between the valve seat ( 3 ) and the valve body ( 5 ). A force ( 19 ) caused by the vacuum acts on the valve body ( 5 ) in a direction towards the closed position. The valve seat ( 3 ) and the valve body ( 5 ) have such a design, that the value of the force ( 19 ), in a continuous way, increases with the degree of opening of the valve body ( 5 ).

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to a vacuum regulator for maintaining asubstantially constant vacuum in a vacuum system, wherein the vacuumregulator comprises a main valve arranged to control a supply of air tothe vacuum system, wherein the main valve comprises a valve seatdefining an passage arranged to lead air to the vacuum system and avalve body moveably arranged in a direction between a closed positionand a maximally open position in order to regulate the size of a minimumflow area between the valve seat and the valve body and wherein a forcecaused by the vacuum acts on the valve body in a direction towards theclosed position

In vacuum systems used in connection with milking machines, it isimportant to maintain a desired constant vacuum in the vacuum system. Inorder to remove the air leaking into the system, a vacuum pump isconnected to the vacuum system having a capacity to maintain more thanthe desired vacuum level in the system. A vacuum regulator is alsoconnected to the vacuum system to supply air to the vacuum system insuch a quantity that the vacuum in the system is maintained at thedesired vacuum level.

Usually, a conventional vacuum regulator comprises a main valvecomprising a valve seat defining a passage arranged to lead air to thevacuum system and a valve cone arranged to control the airflow throughthe passage. An increased degree of opening of the valve cone results ina corresponding increase of the airflow through the passage between thevalve cone and the valve seat to the vacuum system. The vacuum in thevacuum system provides a force acting on the valve cone towards a closedposition. The value of this force depends on the vacuum level and thesize of an active area of the valve cone exposed to the vacuum. Anincreased degree of opening of the valve cone results in an increasedairflow and an increased vacuum acting on the valve cone. That has apositive effect on the force. The active area of a conventional valvecone decreases with an increased degree of opening of the valve cone.The decreased area has usually a greater negative effect on the value ofthe force than the positive effect of the increased airflow.Consequently, the value of the force acting on the valve cone maydecrease or fluctuate in relation to the degree of opening of the valvecone. Thereby, it is difficult to set the valve cone in a desiredarbitrary position with a high precision. Consequently, it is difficultto establish a stable control of the airflow to the vacuum system.

EP 0 017 493 discloses a vacuum regulator comprising a main valvearranged to supply air at a controlled rate to a vacuum system. In thiscase, a spring is arranged to act on a diaphragm connected to a valvemember of the main valve. By means of the spring, the valve member isforced by an additional force against the closed position. Thearrangement of the spring provides an improved stability of the valvemember during the supply of air to the vacuum system.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a vacuum regulator ofthe initial kind, having a valve member with a valve seat and a valvebody having such design that a simple and stable control of the airflowto the vacuum system is obtained.

This object is achieved in that the valve seat and the valve body havesuch design, that the value of said force increases, in a continuousway, with the degree of opening of the valve body. Thereby, it ispossible to create a stable positioning of the valve body in asubstantially arbitrary position. The quantity of air supplied to thevacuum system may be regulated with a high precision, which results in astable and rapid control of the airflow to the vacuum system.

According to a preferred embodiment of the invention, the minimum flowarea is determined by a part of the valve body. The active area of thevalve body on which the vacuum acts is located at the minimum flow areaof the passage. By a suitable design of the valve body and the valveseat, the active area is steadily located at said part of the valvebody. Thereby, the active area is constant independent of the positionof the valve body. Consequently, the active area of the valve body doesnot decrease with an increased degree of opening of the valve body, andthe value of the force is not negatively influenced. Preferably, thelargest radial cross section area of the valve body defines said part ofthe valve body. Thereby, a maximally active area of the valve body isutilised. Advantageously, said part of the valve body is arranged to belocated radially inside the valve seat independent of the position ofthe valve body. Thereby, the valve seat has at least an extensioncorresponding to the distance between the closed and maximally openposition of the valve body. By such a valve seat construction, thelocation of the minimum flow area to said part of the valve body isfacilitated. Preferably, the size of the minimum flow area increases ina continuous way with the degree of opening of the valve body. Thereby,the airflow increases with the degree of opening of the valve body. Theincreased airflow results in an increased vacuum acting on the valvebody. Thus, it is guaranteed that the value of the force acting on thevalve body increases with the degree of opening of the valve body.

According to a further embodiment of the invention, the surface of thevalve seat defines a tapering hole. Such a hole has an increased crosssection area, in a continuous way, toward an inlet of the passage ofvalve seat. Consequently, the minimum flow area between the valve seatand valve body increases when the valve body moves towards an increaseddegree of opening. Advantageously, the valve body has a tapering shape.A tapered valve body provides a simple airtight connection to the valveseat. Furthermore, such a valve body provides a centering of the valvebody in relation to the valve seat. The valve body may have a shape as acone or a frustum of a cone. Preferably, the valve body is movable in anaxial direction in relation to the valve seat. Thereby, the valve bodyis movable along a straight line, which facilitates the control of thevalve body.

According to a further embodiment of the invention, the vacuum regulatorcomprises control means arranged to control the movement of the valvebody. Such control means may control the movement of the valve bodydepending on the actual vacuum in the vacuum system and a desired vacuumlevel in the vacuum system. If the actual vacuum in the vacuum systemincreases, the control means initiates a displacement of the valve bodyfrom the closed position to an open position, and thus air is suppliedto the vacuum system. The degree of opening of the valve body may beregulated in relation to the difference between the actual vacuum andthe desired vacuum.

According to a further embodiment of the invention, such a control meansmay comprise a first diaphragm arranged between a first chamberconnected to the atmospheric pressure and a second chamber connected toa control pressure. The diaphragm is moved against the second chamber ifthe control pressure is lower than the atmospheric pressure. Theposition of the diaphragm is related to the difference between thecontrol pressure and the atmospheric pressure. The valve body obtains,by the connection to the diaphragm, a corresponding position by means ofthe control pressure. A pilot valve may be arranged to regulate thecontrol pressure in the second chamber. Such a pilot valve may beconnected to a second diaphragm arranged between a third chamberconnected to atmospheric pressure and a fourth chamber connected to asignal pressure related to the actual vacuum in the vacuum system. Ifthe actual vacuum in the vacuum system increases in relation to thedesired vacuum, the diaphragm moves the pilot valve to a closedposition. In the closed position, the pilot valve prevents an airflow tothe second chamber. Since, for example, a small conduit connects thesecond chamber to the vacuum the control pressure in the second chamberis gradually reduced. The reduced control pressure results in an openingof the valve body and supply of air to the vacuum system. The supply ofair to the vacuum system proceeds until the pressure in the vacuumsystem reaches the desired vacuum. When the desired vacuum is reachedthe pilot valve opens and air of atmospheric pressure is supplied to thesecond chamber and the valve body moves to the closed position.Preferably, the vacuum regulator comprises adjusting means arranged toenable adjustment of the desired vacuum level in the vacuum system. Suchan adjusting means may comprise a compression spring, which is connectedto the second diaphragm and arranged to compensate for the pressuredifference between the third chamber having atmospheric pressure and thefourth chamber having the actual vacuum. The adjusting means may alsocomprise a tension mechanism arranged to adjust the prestressing of thespring. The adjusting means makes it is possible to adjust the vacuum inthe vacuum system to a desired vacuum level.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by means of apreferred embodiment, which is disclosed as an example, and withreference to the attached drawings.

FIG. 1 shows a vacuum regulator according to the invention,

FIGS. 2a-b shows a conventional main valve in such a vacuum regulatorand

FIGS. 3a-b shows a main valve according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a vacuum regulator 1. The vacuum regulator 1 is arranged tomaintain a substantially constant vacuum level in a vacuum systemcomprising a vacuum pipe 2. Preferably, the vacuum in the vacuum pipe 2is used in connection with a milking machine. In such vacuum systems, itis important to maintain a constant vacuum level. In order to remove theair leaking into the vacuum system, a vacuum pump is connected to thevacuum system. Such a vacuum pump must have capacity to maintain ahigher vacuum in the vacuum system than the desired vacuum level Thevacuum regulator 1 is connected to the vacuum system in order to supplyair to the vacuum pipe 2 in such a quantity that the vacuum in thevacuum pipe 2 is maintained at the desired vacuum level.

The vacuum regulator 1 comprises a main valve arranged to control thesupply of air to the vacuum pipe 2. The main valve comprises a valveseat 3, having a surface defining a tapering hole 4 arranged to lead airto the vacuum pipe 2, and a valve body 5 having a conical shape. Thevalve body 5 is, via a stem 6, connected to a centre part of a firstdiaphragm 7. The first diaphragm 7 is arranged between a first chamber 8having atmospheric pressure and a second chamber 9 having a controlpressure. A pilot valve 10 regulates the value of the control pressure.The pilot valve 10 is connected to a second diaphragm 11. The seconddiaphragm 11 is arranged between a third chamber 12 having atmosphericpressure and a fourth chamber 13 having a signal pressure. A signal pipe14 connects the fourth chamber 13 to the vacuum pipe 2. Therefore, thesignal pressure is identical with the actual vacuum in the vacuum pipe2. A spring 15 acts on the second diaphragm 11. The spring-tension ofthe spring 15 is arranged to compensate for the pressure differencebetween the vacuum in the fourth chamber 13 and the atmospheric pressurein the third chamber 12 when the actual vacuum corresponds to thedesired vacuum level. An adjusting screw 16 is provided at the top ofthe spring 15. The adjusting screw 16 enables a variable adjustment ofthe prestressing of the spring 15 and thereby an adjustment of thedesired vacuum level in the vacuum system.

When the vacuum level in the vacuum pipe 2 is too high in relation tothe desired level, the signal pressure in the fourth chamber 13decreases in a corresponding manner. The decreased signal pressure inthe fourth chamber 13 initiates movement of the second diaphragm 11 inan upward direction against the spring-tension of the spring 15. At thesame time, the second diaphragm 11 displaces the pilot valve 10 to aclosed position. The pilot valve 10 closes the air supply to the secondchamber 9 from the third chamber 12 having atmospheric pressure. A smallconduit 17 connects the second chamber 9 to the signal pipe 14 connectedto the vacuum. Consequently, when the pilot valve 10 is in a closedposition the control pressure in the second chamber 9 decreases and thefirst diaphragm 7 moves in an upward direction. At the same time, thefirst diaphragm 7 displaces, via the stem 6, the valve body 5 to an openposition. The degree of opening of the valve body 5 depends on the valueof the control pressure in the second chamber 9. The value of thecontrol pressure in the second chamber 9 relates to the differencebetween the actual vacuum and the desired level of the vacuum. Thequantity of air supplied to the vacuum pipe 2 depends on the degree ofopening of the valve body 5. The supply of air proceeds until thepressure in the vacuum pipe 2 reaches the desired level. The signalpressure in the chamber 13 increases during the supply of air to thevacuum pipe 2. When the signal pressure has increased to the desiredvacuum level, the second diaphragm 11 moves in a downward direction. Thepilot valve 10 opens and air is supplied to the second chamber 9 and thecontrol pressure increases to the atmospheric level. The increasedcontrol pressure moves the first diaphragm 7 in a downward direction anddisplaces the valve body 5 to the closed position. Thereby, the supplyof air to the vacuum pipe 2 is stopped. As soon as the vacuum dropsagain to a too low level the above-described procedure is repeated inorder to maintain a substantially constant vacuum level in the vacuumpipe 2.

FIGS. 2a and b show a conventional main valve, used in a vacuumregulator 1. The conical valve body 5 has a centre axis a. The conicalvalve body 5 is, in a continuous way, moveable in an axial direction inrelation to the valve seat 3 between a closed position, shown in FIG. 2aand a maximally open position, shown in FIG. 2b, by the movement of thefirst diaphragm 7 according to the explanation above. The quantity ofair supplied to the vacuum pipe 2 is regulated by the degree of openingof the valve body 5. The degree of opening of the valve body 5 isrelated to the size of a minimum flow area 18 of the passage between thevalve body 5 and the valve seat 3. The size of the minimum flow area 18increases in a continuous way with the degree of opening of the valvebody 5. Consequently, an increased degree of opening of the valve body 5provides a corresponding increase of the airflow to the vacuum pipe 2.The vacuum in the vacuum pipe 2 provides a force 19 acting on the valvebody 5 towards the closed position. The value of the force 19 depends onthe vacuum and-the active area 20 of the valve body 5 exposed to thevacuum. The active area 20 of a valve body 5 is located at the minimumflow area between the valve body 5 and the valve seat 3. As seen in FIG.2a-b, the active area 20 of a conventional valve body 5 decreases as thedegree of opening of the valve body 5 increases. An increased air flowresults in an increased vacuum acting on the valve body 5, but theincreased vacuum is not enough to compensate for the decrease of theforce 19 caused by the decreased active area 20. Consequently, the valueof the force 19 acting on the valve body 5 may decrease or fluctuate inrelation to the degree of opening of the valve body 5. Thereby, it isdifficult to position the valve body 5 in an arbitrary desired position.Consequently, it is difficult to control the airflow to the vacuumsystem in a stable way by a conventional main valve.

In FIGS. 3a and b shows a main valve according to the invention. Theconical valve body 5 is, in a continuous way, moveable in an axialdirection in relation to the valve seat 3. In this case, the surface ofthe valve seat 3 defines a tapering hole, which in the embodimentdisclosed is substantially conical. The valve seat 3 has such anextension in an axial direction, that the largest radial cross sectionarea 21 of the valve body 5 is located radially inside the valve seat 3independent of the position of the valve body 5. Thereby, the minimumflow area 18 of the passage between the valve body 5 and the valve seat3 may be located at the largest radial cross section area 21 of thevalve body 5 independently of the position of the valve body 5. Theactive area 20 of the valve body 5, on which the vacuum acts, is locatedat this minimum flow area 18. Consequently, the active area 20 is, inthis case, equal to the largest radial cross section area 21 of thevalve body 5. Thus, the active area 21 is constant and has a maximumsize independent of the position of the valve body 5. Consequently, theactive area 20 of the valve body 5 will not in a negative way influencethe value of the force 19 acting on the valve body 5 during an increaseddegree of opening of the valve body.

The surface of the valve seat 3 has such an inclination in relation tothe surface of the valve body 5, that the circumference of the valvebody 5 engages the valve seat in the closed position. Thereby, theradial distance between the valve body 5 and the valve seat 3 increasesin a continuous way as the degree of opening of the valve body 5 and theminimum flow area 18 increases. Consequently, the airflow increases withthe increased degree of opening of the valve body. The increased airflowresults in higher vacuum acting on the valve body. Thereby, the value ofthe force acting on the valve body will increase as the degree ofopening of the valve body increases.

The invention is not restricted to the described embodiment disclosed inthe figures, but may be varied freely within the scope of the claims.The valve body 5 may, for example, be frusto-conical or shaped as aplate.

What is claimed is:
 1. A vacuum regulator for maintaining asubstantially constant vacuum in a vacuum system, wherein the vacuumregulator comprises a main valve arrange to control a supply of air tothe vacuum system, wherein the main valve comprises a valve seatdefining a passage arranged to lead air to the vacuum system, and avalve body arranged for movement in a direction between a closedposition and a maximally open position in order to regulate the size ofa minimum flow area between the valve seat and the valve body andwherein a force caused by the vacuum acts on the valve body in adirection towards the closed position, wherein the valve seat and thevalve body have a design such that the value of said force increases ina continuous way with the degree of opening of the valve body.
 2. Avacuum regulator according to claim 1, wherein the minimum flow area isdetermined by a part of the valve body.
 3. A vacuum regulator accordingto claim 2, wherein said part of the valve body is defined by thelargest radial cross section area of the valve body.
 4. A vacuumregulator as set forth in claim 3, wherein said part of the valve bodyis arranged to be located radially inside the valve seat independent ofthe position of the valve body.
 5. A vacuum regulator as set forth inclaim 3, wherein the size of the minimum flow area increases in acontinuous way in relation to the degree of opening of the valve body.6. A vacuum regulator as set forth in claim 3, wherein the surface ofthe valve seat defines a tapering hole.
 7. A vacuum regulator as setforth in claim 6, wherein the valve body has a tapering shape.
 8. Avacuum regulator as set forth in claim 7, wherein the valve body ismovable in an axial direction in relation to the valve seat.
 9. A vacuumregulator as set forth in claim 3, wherein the vacuum regulatorcomprises means for controlling the movement of the valve body.
 10. Avacuum regulator according to claim 2, wherein said part of the valvebody is arranged to be located radially inside the valve seatindependent of the position of the valve body.
 11. A vacuum regulatoraccording to claim 1, wherein the size of the minimum flow areaincreases in a continuous way in relation to the degree of opening ofthe valve body.
 12. A vacuum regulator according to claim 1, wherein thesurface of the valve seat defines a tapering hole.
 13. A vacuumregulator according to claim 1, wherein the valve body has a taperingshape.
 14. A vacuum regulator according to claim 1, wherein the valvebody is movable in an axial direction in relation to the valve seat. 15.A vacuum regulator according to claim 1, wherein the vacuum regulatorcomprises control means arranged to control the movement of the valvebody.
 16. A vacuum regulator according to claim 15, wherein the controlmeans is arranged to control the movement of the valve body depending onthe actual vacuum in the vacuum system and a desired vacuum level in thevacuum system.
 17. A vacuum regulator according to claim 16, wherein thecontrol means comprises a first diaphragm arranged between a firstchamber connected to the atmospheric pressure and a second chamberconnected to a control pressure.
 18. A vacuum regulator according toclaim 17, wherein a pilot valve is arranged to regulate the controlpressure in the second chamber.
 19. A vacuum regulator according toclaim 18, including a third chamber connected to atmospheric pressure, afourth chamber connected to a signal pressure related to the actualvacuum in the vacuum system and a second diaphragm connected to thepilot valve, the second diaphragm being arranged between the thirdchamber and the fourth chamber.
 20. A vacuum regulator according toclaim 16, wherein the vacuum regulator further comprises adjusting meansarranged to enable adjustment of the vacuum in the vacuum system to adesired vacuum level.